As internal combustion engines become more fuel efficient, less waste heat is produced, and consequently, the time taken to reach an optimum running temperature increases. This delay in reaching operating temperature may depress fuel economy, increase engine wear and increase exhaust emissions. Additionally, heating systems employed to warm the passenger compartment typically rely on a heater core which is coupled to the coolant jacket of the engine. An increase in engine warm-up time will further result in a delay in warming the passenger compartment, particularly during a cold-start condition.
To enhance engine warm-up conditions, thermal energy storage devices have been developed to store a gas or liquid medium at high operating temperatures. The most common approach has been to employ a phase change material (PCM) that has been exposed to a solid-liquid or liquid-gas change and heat of fusion to optimize the latent heat storage. However, common PCMs may be corrosive to metal, flammable, have low volumetric energy density, may require additional insulation for storage, and the amount of heat stored in the PCM may degrade over time. Hybrid-electric vehicles (HEVs), Plug-in Hybrid Electric Vehicles (PHEVs) and Electric Vehicles (EVs) commonly employ positive thermal coefficient (PTC) heaters and/or fuel fired heaters. Using these systems to warm a passenger compartment may result in large amounts of fuel or electricity diverted from power propulsion systems. Draining the fuel or battery in this manner may severely restrict the driving range of the vehicle.
An example of a heat storage and warm-up control device is shown in U.S. Pat. No. 6,520,136, in which coolant is stored in a heat insulating container as a heat storage device. The coolant may be used to warm an internal combustion engine after passing through an intake air heat exchanger, a heat exchanger for lubricating oil, and a heat exchanger for automatic transmission hydraulic fluid. Japanese patent application 10-77834 discloses a system where coolant stored in a heat storage device may be used for heating engine intake air, engine oil, and automatic transmission fluid. US 2004/0154784 discloses a method for using phase change materials such as paraffin wax in the interior of an vehicle to conserve energy while providing heat to the passenger compartment. However, these systems and methods have similar disadvantages, in that the materials used have low energy density, are highly flammable and prone to losing stored energy over time.
The inventors herein have identified the above issues, as well as systems and methods for a thermal management for a vehicle including an adsorption thermal storage device that allows a high-energy density adsorbent to be used to generate heat for warming the vehicle engine, the passenger compartment, and/or other vehicle elements requiring heat. In one example, a method comprises: during a vehicle engine cold start, opening a first valve coupled between a first container containing an adsorbent and a second container containing an adsorbate, circulating a first fluid through a first conduit coupled to a first heat exchanger located within the first container and a second heat exchanger located outside the first container, and circulating a second fluid through a second conduit coupled to the second heat exchanger. The second conduit may be further coupled to the cooling jacket of a vehicle engine. In this way, heat may be generated at the adsorber during a cold start, such as an engine start with the engine cooled to ambient temperatures, and subsequently transferred to the cooling jacket of the vehicle engine and/or other vehicle compartments, thereby decreasing the warm-up time for the engine or other components.
In another example, a thermal management system for a vehicle, comprises an adsorption thermal storage device comprising a first container including an adsorbent coupled via a first valve to a second container including an adsorbate, a first heat exchanger coupled to the first container and further coupled to a first coolant circuit including a first coolant, and a second heat exchanger coupled to the first coolant circuit and further coupled to a second coolant circuit including a second coolant, a first warming target coupled to the second coolant circuit. In this way, thermal energy may be stored as chemical potential which will not degrade with time. The energy may be accessed by combining the adsorbent with the adsorbate, in this example by opening a valve separating two containers. This system allows heat to be generated without any additional load on the engine, and minimal load on the vehicle battery.
In yet another example, a warm-up system for a vehicle engine, comprises an adsorption thermal storage device comprising an adsorber containing an adsorbent coupled via a valve to a fluid tank containing an adsorbate, a first conduit containing a first coolant, the first conduit coupled to a first heat exchanger located within the adsorber and a second heat exchanger located outside the adsorber, a second conduit containing a second coolant, the second conduit coupled to the second heat exchanger and further coupled to a cooling jacket of the vehicle engine, and a controller configured with instructions stored in memory for: in response to a cold start event, opening the first valve, circulating the first fluid through the first coolant circuit, and circulating the second coolant through the second coolant circuit. In this way, it is possible to utilize an adsorbent and adsorbate to generate heat, high energy density materials such as zeolite may be used to generate a large amount of heat with a small engine compartment footprint, and without resorting to corrosive or flammable materials.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.